Refrigeration system including coated condenser



H. P. HARLE 3,333,562

REFRIGERATION SYSTEM INCLUDING COATED CONDENSER June 18, 1968 FiledSept. 22, 1966 INVENTOR.

HAROLD P. HARLE W H \S ATTORNEY United States Patent 3,388,562REFRIGERATION SYSTEM INCLUDING COATED CONDENSER Harold P. Harle,Louisville, Ky., Assignor to General Electric Company, a corporation ofNew York Filed Sept. 22, 1966, Ser. No. 581,320 3 Claims. (Cl. 62-507)ABSTRACT OF THE DISCLOSURE A refrigerator including a machinerycompartment having a condenser therein. The condenser is coated withmaterial which resists adhesion thereto of foreign substances.

The present invention relates to refrigeration systems including acondenser provided with a coating effective substantially to prevent theadherence to the condenser surfaces of foreign substances carried by anair stream and is more particularly concerned with a householdrefrigerator including a forced air cooled condenser having thereon asurface coating which prevents the accumulation of dust and otherforeign substances on the surface of the condenser.

A relatively large number of household refrigerators include a machinerycompartment containing the condensing component of the refrigerationsystem including a compressor and a relatively compact condenser, and afan for the forced circulation of ambient or indoor air over thecondensing unit for cooling purposes. The condenser usually comprises aserpentine refrigerant tubing provided with a plurality of closelyspaced wire or platetype fins or mounted on or bonded to a sheet ofmetal. It is well known that during operation of a forced air cooledcondenser of this type, foreign substances present in the stream ofhousehold air circulated over the condenser collect on the surfaces andeventually build up to an insulating layer which materially decreasesthe condensing capacity of the condenser.

The collection of such foreign substances on the condenser surfaces andthe eventual clogging of the air passages therein constitutes aparticular problem in the household refrigerator art. The foreignsubstances carried by or comrningled with the household air streampassing over a household refrigerator condenser include not onlyparticulate matter such as lint and dust but also a fluid component,usually an oil or grease, which not only accelerates the collection ofthe particulate component on the condenser surface but also prevents thecirculating air stream from dislodging the lint and dust-like particlesfrom the condenser surface once they have come in contact therewith.Because of this heterogenous composition of the foreign substancespresent in the household air stream, household refrigerator condensersrequire periodic cleaning much more frequently than condensersoperating, for example, in outdoor ambients. In fact, many complaints ofloss of cooling capacity are in fact due only to clogged or coatedcondensers. Therefore, various means have been used or proposed forpreventing the loss of condenser efiiciency resulting in thesecomplaints. However, none of the means heretofore used or proposed havebeen completely satisfactory either from an operational or coststandpoint.

An obvious solution to the problem is the provision of an air filterahead of the condenser. However, because of the limited space availablein a household refrigerator cabinet and particularly because the averageuser forgets that this filter must periodically be changed or cleaned,the provision of a filtering means has usually been found to result inan actual increase, rather than a decrease,

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in such service calls. It has also been proposed to provide a reversiblefan means on the theory that foreign substances filtered from thecirculating air stream as the air flows in one direction will be removedfrom the condenser by the reversed flow of air. However, because theliquid or greasy particles in household air tend to bond the dust andlint particles to the condenser surfaces and to one another the merereversal of the air stream does not serve to dislodge any substantialportion thereof. Another proposed solution to this problem has been theprovision of electrically operated heating means or in other words alint burner ahead of or in contact with the condenser. However, theaddition of such means materially increases the cost of therefrigerator.

The present invention has as its primary object the provision of acondenser having a surface coating of a material which willsubstantially prevent the initial adhesion of foreign substances presentin household air to the condenser surfaces and thereby prevent thecontinuing accumulation of such foreign substances on the condenserstructure.

Further objects and advantages of the invention will become apparentfrom the following description thereof and the features of novelty whichcharacterize the invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

In accordance with the present invention, a condenser is provided with asurface coating which resists the adhesion thereto of foreign substancescarried by a household air stream and thereby effectively prevents thecontinued accumulation of such foreign substances on the condenserstructure. More specifically, a condenser of the household refrigeratortype comprising a plurality of spaced transverse tubular refrigerantconduits and a plurality of spaced longitudinally extending fins isprovided with a substantially continuous surface coating of a polymerselected from the group consisting of polytetrafluoroethylene,polyhexafluoropropylene and copolymers of tetrafluoroethylene andhexafiuoropropylene.

For a better understanding of the invention reference may be had to theaccompanying drawing in which:

FIGURE 1 is a vertical sectional view of a portion of a householdrefrigerator including the improved condenser of the present invention;and

FIGURE 2 is an enlarged sectional view of the condenser taken generallyalong line 22 of FIGURE 1.

With reference to the drawing, there is shown a household refrigeratorincluding a storage compartment 1 designed to be maintained atrefrigerating temperatures by means of an evaporator (not shown) formingpart of a refrigeration system and a machinery compartment 2 at thelower portion of the cabinet for containing the condensing component ofthe refrigeration system including a compressor 3 and a condenser 4. Itis to be understood that the compressor 3, the condenser 4 and theevaporator are connected by suitable conduits to form a closedrefrigerant circuit including suitable fiow restricting means betweenthe compressor and evaporator.

In the illustrated cabinet, the machinery compartment 2 is divided intotwo sections by means of a longitudinally extending partition 5 runninggenerally from the rear wall 6 of the refrigerator cabinet to the frontwall 7. A fan 8 mounted in the rear portion of the partition 5 draws astream of household air inwardly through one side of a grille 9 providedat the lower front portion of the cabinet into cooling relationship withthe condenser 4 and the compressor 3 and discharges the air back intothe room through the other end of the grille 9.

The illustrated condenser 4, as is more clearly shown in FIGURE 2 of thedrawing, is made by forming a continuous tube into a serpentine form toprovide a structure including a plurality of spaced transverserefrigerant conduits 11 series connected by means of lU-shaped end turns12. In order to provide a compact structure, the passes 11 are arrangedin a plurality of sections or tiers, three in number as shown in FIGURE2. The passes 11, in each of these tiers are provided with additional orsecondary heat transfer surface in the form of a plurality of closelyspaced parallel wires 14 extending perpendicular to the passes 11 or inother words longitudinally of the evaporator structure. Preferably wires14 are secured to both the upper and lower surfaces of the passes ineach of the tiers.

During operation of the fan 8, any foreign substances suspended in theroom or household air are circulated along with the air stream intocontact with the surfaces of the condenser 4. A few of these particlesof the dry or lint type become lodged in the crevices or recessesbetween a pass 11 and a wire or wires 14 but such collected particles donot materially interfere with the efliciency of the condenser. The majorloss in condenser efiiciency results from the deposition on and readyadherence to the otherwise smooth or continuous condenser surfaces,including both the surfaces of the passes 11 and the surfaces of thefins or Wires 14, of a continuation of the fluid and lint types ofsubstances and the continuous accumulation of such foreign substances toform a relatively thick insulating layer of foreign substances on thecondenser surfaces. This accumulation has been found to result from thepresence of the high proportion of the oily or greasy components inhousehold air which may be in the range of 22 percent by weight of thetotal foreign substance contents as compared with from to 13 percent ofsuch oily materials in vacuum cleaner dirt or dirt suspended in theaverage outdoor atmosphere.

In other words, while the collection of inert particulate matter and airborne fiber fragments on a condenser surface may be caused by bothmechanical entrapment and adhesion, adhesion due to the presence of theoil fluid components is the principal factor. The present invention isbased in part of the discovery that the retention of the oil componentis strongly dependent upon the nature of the surface contacted thereby.

In accordance with the invention, the adhesion and retention of oilbonded lint and dust by virtue of an intervening oil film which wetsboth these soil particles or fiber residues and the surface issubstantially prevented by providing a condenser surface designed toreduce the oil adhesion and also to reduce the degree of spreading ofany oil film on that surface. It has been found that the highlyfiuorinated polymers and copolymers are particularly effective for thispurpose. More specifically, it has been found that the polymers of fullyfluorinated polyethylene and polypropylene or copolymers thereof aremost effective in reducing the adhesion to the condenser surface of oilair borne particulate mixtures.

Therefore in accordance with the present invention, the condenser 4 isprovided with an exterior coating of a material such aspolytetrafluoroethylene, or polyhexafluoropropylene or copolymers of thetetrafiuoroethylene and hexafiuoropropylene, such a coating beingindicated in FIGURE 2 of the drawing by the numeral 15.

This dust and grease resistant coating may be applied to the condensersurfaces by any of the well known methods used for coating metalsurfaces with the above enumerated materials. For example, the coatingsmay be applied to the finished condenser structure by a spray-- ing ordipping process employing a suspension of the finely divided polymer orpolymers although in the manufacture of some condenser structures as forexample the metal plate fin-on-tube condenser, the individual componentsthat is the individual plate-type fins and the tubing may be pre-coatedprior to the assembly of the fins on the tubing.

While surfaces composed of the subject polymers and copolymers are wellknown for their non-adhesive p operties as shown for example by theextensive use of polytetrafiuoroethylene in the greaseless fry pan andrelated cooking utensil art their effectiveness in preventing theadhesion of air borne foreign substances to a condenser surface was fargreater than would have been expected from their known uses. Forexample, a wire fin-on-tube condenser of the construction illustrated inthe drawing having no surface coating or merely a corrosion protectivepaint surface coating of black enamel, when subjected to an acceleratedtest to determine the amount of air borne dust composed primarily ofoily lint and dust accumulated thereon in test conditions to simulatefive years of actual usage in a home became completely clogged with suchforeign substances.

On the other hand, the same condenser structure provided with acontinuous surface coating of polytetrafluoroethylene when subjected tothe same test did not become clogged and in fact had thereon only a verythin film of deposited particles of a thickness such that the surfacesof the condenser was still apparent through the layer. The amount ofaccumulation on the treated condenser surfaces was less than percent ofthe amount collected on the untreated surfaces.

While there has been shown and described a particular embodiment of thepresent invention it will be understood that it is not limited theretoand is intended by the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A household refrigerator comprising a machinery compartment and arefrigeration system including an air cooled condenser disposed in saidcompartment and forced air circulating means for circulating a stream ofair through said compartment and over said condenser,

said condenser comprising a plurality of spaced transverse tubularrefrigerant conduits and a plurality of spaced longitudinally extendingfins connected to said conduits,

said condenser exterior surface being coated with a polymer selectedfrom the group consisting of polytetrafluoroethylene,polyhexafluoropropylene and copolymers of tetrafiuoroethylene andhexafluoropropylene whereby the adherence of foreign substances carriedby said stream of air to said surface is substantially reduced.

2. The refrigerator of claim 1 in which said polymer ispolytetrafluoroethylene.

3. The refrigerator of claim 1 in which said machinery compartment is inthe lower part of said cabinet.

References Cited UNITED STATES PATENTS 3,079,770 3/1963 Brown 62-507 XR3,341,348 9/1967 Letendre 117132 FOREIGN PATENTS 972,129 10/ 1964 GreatBritain.

MEYER PERLIN, Primary Examiner.

